This invention relates to an X-ray radiography apparatus for forming X-ray images on a plurality of imaging medium sheets removed, one by one, from a supply magazine, and more particularly, to an apparatus which can not only form X-ray images on the sheets but also display the number of unexposed sheets remaining in the supply magazine.
FIG. 1 shows a conventional X-ray radiography apparatus for forming X-ray images on a plurality of imaging medium sheets removed, one by one, from a supply magazine. This apparatus has supply magazine 1 containing a stack of imaging media, or sheet films 2. Suction cup 3 made of soft material, such as rubber, is provided above magazine 1. Cup 3 is repeatedly moved up and down, and also to the left to the right, and vice versa, thereby removing films 2, one by one, from the upper side of magazine 1. More specifically, cup 3 is moved down, contacts the topmost film 2, attracts this film to it, and is moved up, thereby drawing the film from magazine 1 through the opening cut in the upper side of magazine 1. Still holding sheet film 2, cup 3 moves to the vicinity of a pair of conveying rollers 4, whereupon the end of film 2 is nipped therebetween.
The apparatus further comprises film holder 5 provided on the output side of rollers 4. Holder 5 has a pair of plates 5A and 5B hinged at one side, such that holder 5 can open and close. A sensitized sheet is bonded to an inner surface of each of plates 5A and 5B. Holder 5 is usually open to receive sheet film 2 from rollers 4. It is closed upon receipt of film 2, as plate 5A is rotated in the direction of arrow B, thereby holding sheet film 2.
Thereafter, film 2, which is held by holder 5, remains in waiting position 6A until the operator commands an image-forming operation to be performed.
When the operator gives an image-forming command, film holder 5 is moved rapidly to imaging position 7A. In position 7A, an X-ray image of patient
on bed BT is formed on sheet film 2 held by holder 5 as patient PA is exposed to the X rays emitted from X-ray tube XT. After the image-forming operation has been completed, holder 5 is returned to waiting position 6A, whereupon it is opened. Then, conveying rollers 4 are rotated in the reverse direction. The exposed film in holder 5 is nipped between reversely rotating rollers 4, and is thus fed from rollers 4. At this time, direction-switching member 8, provided near rollers 4 and hinged to shaft 8A, is rotated around shaft 8A in the direction of arrow E (FIG. 1). As a result, exposed film 2, fed from rollers 4, is guided by member 8 into guide passage 9, and is fed therethrough into magazine 10 situated below supply magazine 1.
Most X-ray radiography apparatus of this type are provided with a TV camera (not shown) and a CRT (Cathode Ray Tube) display (not shown, either), in order to pick up X-ray images and display them. That is, the TV camera receives the X-ray images detected by an image intensifier (I.I.) provided behind imaging position 7A, and the CRT display displays these X-ray images.
The operator sees the X-ray images displayed, one after another, on the CRT display, and gives an imageforming command the moment the CRT display shows the image he or she desires. In accordance with this command, the apparatus forms the X-ray image on sheet film 2.
Supply magazine 1 can contain 50 to 100 unexposed sheet films 2 at most. Since magazine 1 is provided within the housing of the apparatus, the operator cannot know how many unexposed films 2 are left in magazine 1 unless he or she pulls magazine 1 out of the housing and looks into it. To confirm the number of films remaining in magazine 1, the operator must record the number of films 1 before starting the image-forming operation, then count exposed films 2, and subtract the count from the number of films 2 stored in magazine 1 before the image-forming operation. This method is cumbersome and is unreliable and, since it is very difficult for the operator to accurately count unexposed films 2 stored in magazine before the image-forming operation and to correctly count exposed films 2 during the operation. Unless the number of films 2 remaining in magazine 1 can be confirmed, various problems will arise. Sometimes, the contrast medium, injected into patient PA to obtain a clear-cut X-ray image of a region of interest, reaches the region shortly after the last unexposed film supplied from magazine 1 has been exposed. In this case, the operator must pull magazine 1 from the housing of the apparatus, fill it with unexposed films 2, and insert it back into the housing. When the first of the refilled films 2 reaches imaging postion 7A, the contrast medium has alreadly been drained from the region of interest, and the medium must be injected again into patient PA, particularly in the case of angiography. To obtain a clear-cut X-ray image of the stomach, patient PA must be moved again, such that the medium injected again reaches the region of interest. Hence, some measures should be taken to allow the operator to known how many unexposed films 2 remain in supply magazine 1.
To this end, a device, which can detect when the number of films remaining in a magazine has been reduced below a predetermined value, has been proposed in Japanese Patent Disclosure No. 57-114134. The device has an optical fiber for guiding light from a light source to a suction unit (i.e., a suction cup), and a photodetector provided on the side wall of the magazine. The photodetector is positioned such that the light-emitting end of the optical fiber is optically coupled to the photodetector when the number of the remaining films is reduced to the predetermined value. Hence, when the photodetector receives the light guided by the fiber, it can detect that the number of the films left in the magazine has just been reduced to a predetermined value. This device, however, cannot detect how many unexposed films 2 are thereafter left in magazine 1. Another problem with the device is that the photodetector must be connected to a detection circuit by a connecting wire.